Chloroiminium Salts Research Articles

The interaction of molybdenum pentachloride with carbonyl compounds

The reactions of MoCl(5), 1, with small amounts of a series of carbonyl compounds in a chlorinated solvent were investigated. The chloroiminium salts [ClCH=NEt(2)][Mo(O)Cl(4){O=C(H)NEt(2)}], 2a, and [ClC=NH(CH(2))(4)CH(2)][Mo(O)Cl(4){O=CNH(CH(2))(4)CH(2)}], 2b, were obtained by a selective 1 : 2 molar reaction of 1 with, respectively, N,N-diethylformamide or ε-caprolactam. Otherwise 1 reacted with tetra-N-alkyl ureas in a 1 : 2 ratio to give the Mo(IV) mononuclear complexes MoCl(4)(urea)(2) [urea = (Me(2)N)(2)CO, 3a; urea = (Et(2)N)(2)CO, 3b; urea = (EtPhN)(2)CO, 3c] in high yields. Addition of 2 equiv. of ketones to 1 resulted in clean formation of equimolar amounts of MoOCl(3)(O=CR(2)) (R = Me, 4a; R = Et, 4b; R = Ph, 4c) and R(2)CCl(2). Analogously 1,2-C(6)H(4)(Me)(CHCl(2)) was produced from MoCl(5) and ortho-tolyaldehyde. The reactions of 1 with 1H-indole-2,3-dione (isatin) took place with selective chlorination of the carbonyl function non-adjacent to the nitrogen: the complexes MoOCl(3)(3,3-dichloro-2,3-dihydro-1H-indol-2-one)(2), 5a, and MoOCl(3)(isatin)(3,3-dichloro-2,3-dihydro-1H-indol-2-one), 5b, were isolated depending on the stoichiometry employed. The X-ray molecular structures of 2b, 3b, 4b, 5a and 5b were ascertained.

Lactam/MoCl5 interaction in CH2Cl2: synthesis and X-ray characterization of protonated δ-valerolactam salts

The protonated lactam salts , 1, , 2, and , 3, were isolated from the non selective reaction of MoCl5 with δ-valerolactam in dichloromethane, carried out with different molar ratios. The 1:2 reaction of MoCl5 with N-methyl-2-pyrrolidone afforded the chloroiminium salt , 4, in 74% yield, together with minor amount of , 5. The products 1–5 were characterized by analytical and spectroscopic techniques, and by X-ray diffractometry in the cases of 1 and 3.

Bulky Acyclic Aminooxycarbene Ligands

A series of sterically demanding acyclic aminooxycarbenes (AAOCs) were prepared in good yields from chloroiminium salts and alkoxysilanes via the TMS-Cl elimination pathway. The steric profiles of bulky AAOCs were determined by X-ray crystallographic studies of the Au(I) complexes. The percent buried volume values (%VBur) of the AAOC ligands range from 35.8% to 47.9%. Acyclic aminooxycarbenes maintain coplanarity around the carbene center, in sharp contrast to the similarly bulky acyclic diaminocarbenes that show significant distortion from the coplanarity. The Au(I) complexes of AAOCs exhibited high efficiency in the hydroamination of alkenyl ureas. Bulkier AAOC–Au(I) complexes displayed faster reaction rates and higher conversions. The reaction rate, yield, and stereoselectivity observed with the AAOC–Au(I) catalyst were better than those with acyclic diaminocarbene Au catalysts and comparable to the best results reported to date.

C−N Bond-Forming Self-Condensation of Amide Promoted by MoCl5 at Room Temperature

The acylamidinium complex MoOCl(4)[MeC(O)N(Ph)C(Me)═NHPh] (2) was obtained by selective self-condensation of MeC(O)NHPh promoted by MoCl(5). Otherwise, the stable chloroiminium salt [MoOCl(4){HC(O)NMe(2)}][CH(Cl)═NMe(2)] (3) was isolated from HC(O)NMe(2)/MoCl(5).

Telluration of seleno- and chloroiminium salts leading to various telluroamides, and their structure and NMR properties

The reaction of seleno- and chloroiminium salts with a tellurating agent derived from LiAlH 4 and elemental tellurium gave telluroamides in moderate to good yields. This new synthetic method enabled the isolation of the first aliphatic and secondary telluroamides. The molecular structure of an aromatic telluroamide was successfully revealed for the first time; the length of the C Te bond in the aromatic telluroamide was the same as that in the telluroformamide–Cr complex, and the aromatic ring and Te C–N moiety were not planar. Unlike the structure in the solid state, spectroscopic data of telluroamides suggest that there is conjugation between these two planes. The properties of the NMR spectra of a series of chalcogenoamides are also discussed.

New synthetic routes to C-amino phosphorus ylides and their subsequent fragmentation into carbenes and phosphines.

Phosphonio-substituted aldiminium, iminium, and imidazolidinium salts are readily prepared by the addition of phosphines to the Alder dimer or by treatment of the corresponding chloroiminium salt with the phosphine/trimethylsilyl triflate adduct generated in situ. Reduction with either potassium metal or tetrakis(dimethylamino)ethylene leads to the corresponding C-amino phosphorus ylides. When basic phosphine fragments are used, the ylides can be isolated; otherwise they fragment into the carbene and phosphine. This method is limited to the preparation of transient carbenes, owing to the unavailability of sterically hindered dications, and consequently of phosphorus ylides with bulky carbon substituents. This difficulty is overcome by the addition of 2,4-di-tert-butyl-ortho-quinone to readily available C-amino phosphaalkenes at low temperature. Provided the phosphorus atom bears either an amino or tert-butyl group, [4+1] cycloaddition occurs, and the resulting ylides fragment into a dioxaphospholane and a spectroscopically observed carbene.

A One‐Step Route to Azomethine Ylides via Chloroiminium Salts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Facile Conversion of Amides and Lactams to Selenoamides and Selenolactams Using Tetraethylammonium Tetraselenotungstate.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A one-step route to azomethine ylides via chloroiminium salts

A new, one-step procedure for the generation of azomethine ylides, 4 and 20 , via chloroiminium salts, 3 and 19 , is reported. The generation of the azomethine ylides was confirmed by their trapping with dimethyl acetylenedicarboxylate (DMAD) which, upon spontaneous 1,4-dehydrochlorination, gave the corresponding pyrroles 17 and 21 .

Facile conversion of amides and lactams to selenoamides and selenolactams using tetraethylammonium tetraselenotungstate

Chloroiminium salts generated in situ from amides and lactams using (COCl) 2 or POCl 3 react very readily with the new selenium transfer reagent, tetraethylammonium tetraselenotungstate, (Et 4N) 2WSe 4, 1 , to afford the corresponding selenoamides and selenolactams in excellent yields under mild reaction conditions.

New Methods of Synthesis of Phosphoryl and Thiophosphoryl Halides from Organylchlorophosphonium Hexachlorophosphorates

A new method of synthesis of phosphonic and thiophosphonic chlorides is offered, based on treatment of acyclic and cyclic organylchlorophosphonium hexachlorophosphorates with dimethylformamide, dimethylacetamide, or dimethylthioacetamide. The method involves no formation of phosphoryl chloride and thiophosphoryl chloride, which facilitates isolation of the target products. The reactions of alkenylchlorophosphonium hexachlorophosphorates with amides and thioamides results in incorporation of the PCl6- anion into an insoluble chloroiminium salt which is easily separated by filtration. Removal of the solvent leaves almost pure phosphonic or thiophosphonic chlorides.

Iminiumsalze in quantitativen Gas/Festk�per- und Festk�rper/Festk�rper-Reaktionen

Iminium Salts in Quantitative Gas/Solid and Solid/Solid Reactions Iminium salts that are highly susceptible to hydrolysis are quantitatively prepared and reacted in the solid state without solvents or liquid phases. Atomic force microscopy AFM helps in elucidating the mechanism of these still unusual gas-solid and solid-solid syntheses by recording surface topographies of reacting crystals of L-histidine (10) and triphenylverdazyl (15). Various imines add gaseous HCl or HBr to form stable iminium halides (1, 3, 4, 5, 11) even if frozen liquids of very weak heterocyclic bases are treated at low temperatures. Another way for quantitative yields of iminium salt hydrates (6) starts with solid primary ammonium halides and gaseous acetone. o-Phenylenediamines (7) give quantitatively 1,5-benzodiazepines (9) by solid state cyclization of bis-iminium salt intermediates (8). Crystalline nitroxyls (12) and triphenylverdazyl (15) undergo stoichiometric one-electron transfer with gaseous NO2 or XeF2 to give nitrosonium (14) and azonium salts (17). The solid state chlorination of tetramethylthiuramdisulfide (18) or dimethylthiocarbamoylchloride (20) yields phosgene dimethyliminiumchloride (Viehe salt 21) in quantitative yield. Solid Viehe salt is quantitatively treated with gaseous Cl2 to give the trichloride 19 and solid SbCl5 or PCl5 to produce the hexachloroantimoniates (22), -phosphates (23). Solid brenzcatechol (24), mercaptobenzimidazole (27), p-nitroaniline (30), N-methylbenzothiazolone-2-hydrazone (34) and acetophenone (41) are treated with 21 to give the corresponding chloroiminium salts (25, 28, 31, 35, 43). p-Toluenesulfonamide (37) and 22 give the chloroiminium salt 38. These quantitative solid-solid reactions are most easily run in ball mills with cooling device. The “waste-free” techniques achieve exclusion of moisture in an elegant way. The preparative use of the versatile products with nucleophiles is indicated. The three-step solid-state mechanisms are discussed.

A Facile Conversion of Amides and Lactams to Thioamides and Thiolactams using Tetrathiomolybdate

Chloro iminium salts generated in situ from amides and lactams using (COCl) 2 or POCl 3 reacted very readily with the new sulfur transfer reagent, benzyltriethylammonium tetrathiomolybdate to afford the corresponding thioamides and thiolactams in exellent yields under mild reaction conditions.

Etude par RMN du mecanisme des reactions de transcomplexation entre les sels de chloroiminium (reactifs de vilsmeier) et les amides ou thioamides. Appl

Previous studies have established the existence of an acid-base equilibrium between the Vilsmeier complex (Me 2NCHCl) + B − and dimethylformamide. It is shown that the behaviour of chloroiminium salts as Lewis acids towards amides or thioamides is a general phenomenon. When the acids and bases are differently substituted, the reaction may have synthetic applications.

Nuclear magnetic resonance investigations of carbonium ion intermediates. Part II. Exchange reactions in chloro-iminium salts (Vilsmeier–Haack reagents)

Different kinds of coalescence phenomena have been observed for solutions of chloro-iminium salts. The rate of the exchange mechanism is concentration dependent. An acid–base equilibrium between the Vilsmeier complex (Me2NCHCl)+B– and the dimethylformamide is evident. Thermodynamic and kinetic parameters have been calculated for different solvents and different anions B– by total line shape analysis of continuous wave and Fourier transform spectra.

Pyranylidene iminium salts II. Iminium salts derived from pyrones, dialkylamides and phosphorus oxychloride

AbstractN,N‐Dialkylamides, pyrones, and phosphorus oxychloride react to give pyranylidene chloroiminium salts. The chlorine atom of these salts is readily displaced by nucleophiles to yield a variety of pyranylidene derivatives.